The present invention is directed towards a growth medium for plants. The present invention is also directed towards a growth medium for use as a casing soil in mushroom cultivation.
In commercial mushroom cultivation it is general practice to provide a lower layer of compost which is covered by a layer of a material referred to as casing soil. It is important in mushroom cultivation that the casing soil assists in maintaining a desirable moisture level for mushroom growth. It should also maintain a desirable carbon dioxide and oxygen ratio. Further the casing soil should maintain the nutrient balance of the compost and also act as a barrier to disease and insect pests.
To date, the only material which has been recognised by commercial mushroom growers as being acceptable for use as casing material is sphagnum peat. Sphagnum peat is partially decomposed sphagnum moss and is obtained from Ireland, Holland and Canada (known as blonde peat). Sphagnum peat has the required ability to retain moisture at levels suitable for mushroom growth, together with required porosity and nutrient levels.
However, existing sphagnum peat supplies are becoming depleted. Thus, there is a need in the industry for an alternative to sphagnum peat. Still further, the costs of obtaining imported sphagnum peat are high and adds considerably to a mushroom grower""s costs. Thus, there is a further need in the industry for an economically viable alternative to sphagnum peat.
A difficulty with obtaining an alternative to sphagnum peat is that any alternative must satisfy the particular requirements for mushroom cultivation. As mentioned above, a casing soil must have a moisture holding capacity to ensure that there is sufficient moisture to support mushroom growth Other important properties include neutral pH, low salt levels and suitable nutrient levels. It has been observed that although other types of peat such as sedge peat are available they do not satisfy the above requirements and are unsuitable as casing soils. To date, there is no commercially available alternative to sphagnum peat.
In the horticultural industry, it is common practice to prepare artificial growth medium for use as potting mixes. Such growth media must have desirable air porosity, water retention properties and sufficient nutrients to sustain plant growth.
Typical commercial potting mixes include a mixture of coarse sand and an organic material. Such a mixture on its own is generally deficient in many nutrients necessary for plant growth. Thus, to provide a satisfactory mix, it is necessary to add the nutrients required for plant growth.
Typical organic materials are timber products such as bark chips and composted bark material. Although these materials are generally obtained from byproducts of timer production, their supply does rely on diminishing natural resources.
In an attempt to provide a plant growth medium with desirable properties a number of different combinations of material have been researched. Examples of these earlier studies include the use of filler materials such as bagasse, coconut fibre and rice husks with sphagnum peat moss and sphagnum peat.
Filler materials such as bagasse are fibrous materials which contain no significant levels of nutrients. Thus, it is necessary to add the nutrient rich sphagnum moss or peat. However, as mentioned above, sphagnum peat is in a finite supply. To date, it is believed there is no acceptable alternative to the use of sphagnum peat in the horticulture or mushroom industries.
It is therefore an object of the present invention to provide a growth medium for plants and mushrooms which may at least partially overcome the above disadvantages or provide the public with a useful choice. It is also an object of the present invention to provide a material for use as a casing soil which may be used as an alternative to sphagnum peat
According to a first broad form of the invention there is provided a growth medium for plants or mushrooms, the medium comprising sugarcane mill mud and a non-sphagnum peat material selected from the group consisting of a non-sphagnum peat and coconut fibre.
The growth medium of the present invention may be used in a wide range of applications including potting mixes, soil additive, mulch, mushroom casing soil and also as a top dressing material for germination of grass seeds.
In the present specification and claims, the term xe2x80x9cnon-sphagnum peatxe2x80x9d includes any peat material which is not derived from sphagnum moss. Such peat materials include peat derived from sedges or trees. Another suitable material is coconut fibre, which is known as coco peat. Typically, coco peat consists of shredded coconut coir (the fibrous part of a coconut shell). The coconut fibre may be either partially composted or used in its raw state. Combinations of any two or more types of peat and/or coconut fibre may also be used. Sphagnum peat may also be included as a minor component of the composition if desired.
The term xe2x80x9csugarcane mill mudxe2x80x9d in the present specification and claims refers to washing material from sugar cane mills. The washings include cane washings, lime, cane juice impurities and fine bagasse.
Neither non sphagnum-peat materials or sugarcane mill mud when used exclusively as a plant growth medium or casing soil are suitable for satisfactory plant or mushroom growth. However, the present inventor has surprisingly discovered that when a sugarcane mill mud and non-sphagnum peat are used in combination, a material suitable for use as a plant growth medium or casing soil may be obtained.
Neither product on its own is suitable for satisfactorily supporting plant or mushroom growth.
The ratio of non sphagnum-peat material to sugarcane mill mud is typically between about 1.4:1 to about 2:1 parts by weight. Preferably the ratio is about 1.7:1. The amount may vary depending upon the type of peat and source of the sugarcane mill mud. For example, the composition of the sugar cane mill mud may vary, depending upon the source mill.
Typically, the respective amounts of sugar cane mill mud and non sphagnum-peat material component are selected so as to optimise desirable properties such as water retention, aeration, pH, salt content and nutrient level. For example, non sphagnum-peat materials typically have undesirable properties such as low pH, low nutrient levels and low air porosity. These properties may be offset by the sugarcane mill mud which has near neutral pH, suitable nutrient levels and good air porosity. Conversely, undesirable properties of the sugarcane mill mud such as high salt levels, low moisture retention, high levels or susceptibility to unwanted biological organisms are offset by the non sphagnum-peat material which was as low salt levels, good moisture retention and is substantially free of nematodes and other soil pathogene.
Preferably, the non sphagnum-peat material sugarcane mill mud are mixed to provide a composition having the ranges as defined in the following Table 1.
When used as a casing soil composition, preferably water is also added to the peat and/or coconut fibre sugarcane mill mud mixture to provide a water content of between about 65-75% (wt/vol). Typically, the casing soil composition is sterilised prior to use. Other optional additives may also be added. Such additives include wetting agents, fungicides, nematicides, insecticides and texture and pH controlling agents. Such additives are known to those skilled in the art. The composition may also be supplemented with nutrients, if desired, such that the concentrations of the respective chemicals fall within the ranges in Table 1.
Where the medium is to be used as a plant growth medium such as potting mix or top dressing soil, it ma be desirable to add a filler material to modify porosity and/or water retention. The amount of filler can be varied, depending upon the desired properties of the mix. This can depend on the type of plant to be grown. Suitably, about 30 to about 80 wt % of filler may be added. Potting mixes will typically include about 60 to about 70 wt % filler where top dressing soils can contain lower levels of filler.
A preferred filler is an inert material. An especially preferred filler is bagasse.
Optionally, further additions known in the art may be added to the medium of the present invention. Such additives include wetting agents, insecticides, nematicides, nutrients and a pH modifying agent.